A systematical study on the relationship between the amounts of different eutectic phases especially the low-melting-point(LMP)eutectics and the hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidificat...A systematical study on the relationship between the amounts of different eutectic phases especially the low-melting-point(LMP)eutectics and the hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification was performed.By controlling the concentrations of major alloying elements(Cu,Mg),the amounts of LMP eutectics at the final stages of solidification were varied and the corresponding hot tearing susceptibility(HTS)was determined.The results showed that the Al−4.6Cu−0.4Mg(wt.%)alloy,which contained the smallest fraction of LMP eutectics among the investigated alloys,was observed to be the most susceptible to hot tearing.With the amount of total residual liquid being approximately the same in the alloys,the hot tearing resistance is considered to be closely related to the amounts of LMP eutectics.Specifically,the higher the amount of LMP eutectics was,the lower the HTS of the alloy was.Further,the potential mechanism of low HTS for alloys with high amounts of LMP eutectics among ternary Al−Cu−Mg alloys was discussed in terms of feeding ability and permeability as well as total viscosity evolution during solidification.展开更多
Interfacial energy anisotropy plays an important role in tilted growth of eutectics. However, previous studies mainly focused on the solid-solid interface energy anisotropy, and whether the solid-liquid interface ener...Interfacial energy anisotropy plays an important role in tilted growth of eutectics. However, previous studies mainly focused on the solid-solid interface energy anisotropy, and whether the solid-liquid interface energy anisotropy can significantly affect the tilted growth of eutectics still remains unclear. In this study, a multi-phase field model is employed to investigate both the effect of solid-liquid interfacial energy anisotropy and the effect of solid-solid interfacial energy anisotropy on tilted growth of eutectics. The findings reveal that both the solid-liquid interfacial energy anisotropy and the solid-solid interfacial energy anisotropy can induce the tilted growth of eutectics. The results also demonstrate that when the rotation angle is within a range of 30°-60°, the growth of tilted eutectics is governed jointly by the solid-solid interfacial energy anisotropy and the solid-liquid interfacial energy anisotropy;otherwise, it is mainly controlled by the solid-solid interfacial energy anisotropy. Further analysis shows that the unequal pinning angle at triple point caused by the adjustment of the force balance results in different solute-diffusion rates on both sides of triple point. This will further induce an asymmetrical concentration distribution along the pulling direction near the solid-liquid interface and the tilted growth of eutectics. Our findings not only shed light on the formation mechanism of tilted eutectics but also provide theoretical guidance for controlling the microstructure evolution during eutectic solidification.展开更多
Under the cold-chamber high pressure die casting (HPDC) process, samples were produced with AM60B magnesium alloy to investigate the microstructure characteristics of the eutectics, especially focusing on the constitu...Under the cold-chamber high pressure die casting (HPDC) process, samples were produced with AM60B magnesium alloy to investigate the microstructure characteristics of the eutectics, especially focusing on the constitution, morphology and distribution of the eutectics over cross section of the castings. Attentions were also paid to study the effect of heat treatment on the eutectics in the die castings. Based on experimental analysis using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), it was determined that fully divorced eutectics consisting of c^-Mg and l%MglzA112 appeared at the grain boundary of the primary c^-Mg in the as-cast microstructure. Islands and networks of β-Mg17Al12 phase were observed in the central region of the castings, while the β-Mg17Al12 phase revealed a more dispersed and granular morphology on the surface layer. The two phases ratio β/α in the central region of the castings was approximately 10%, which was higher than that on the surface layer. Besides, the defect bands contained a higher percentage of the eutectics than the adjacent regions. After aging treatment (T6), only α-Mg phase was detected by XRD in the AM60B magnesium alloy, though a small amount of precipitated β-MgITAI12 phase was observed at the grain boundary. In contrast to the microstructure of die cast AZ91D magnesium alloy under the same T0 heat treatment, no discontinuous precipitation of the β-MgITAI12 phase was observed in AMO0B magnesium alloy die castings.展开更多
A new steel matrix wear resistant composite reinforced by in situ granular eutectics can be obtained by modifying with a Si-Ce-Ti compound in the steel melt. The result indicates that the in situ granular eutectic is...A new steel matrix wear resistant composite reinforced by in situ granular eutectics can be obtained by modifying with a Si-Ce-Ti compound in the steel melt. The result indicates that the in situ granular eutectic is a pseudo-eutectic of austenite and (Fe,Mn)3C, which is formed between austenite dendrites during solidification due to the segregation of C and Mn impelled by modifying elements. The quantity of in situ granular eutectic reaches up to 8%-12% and its grain size is in the range from 10um to 20um. The austenite steel matrix wear resistant composite reinforced by in situ granular eutectic (abbreviated AGE composite) and austenite-bainite steel mains wear resistant composite reinforced by in situ granular eutectic (abbreviated ABGE composite) are obtained in the as-cast state and by air hardening, respectively. The wear resistance of the AGE and ABGE composites can be more greatly increased than that of their matrix steels under low and medium impact working condition.展开更多
1.Introduction As an ancient method for manufacturing metallic materials,casting has the advantages of low cost,high process flexibility and forming complex parts.However,due to the poor as-cast mechanical properties,...1.Introduction As an ancient method for manufacturing metallic materials,casting has the advantages of low cost,high process flexibility and forming complex parts.However,due to the poor as-cast mechanical properties,various processes after casting are generally necessary for traditional metallic materials to eliminate casting defects(e.g.,voids,shrinkage cavities and elemental segregation)and improve their properties,such as rolling,forging,and heat treatment.展开更多
This paper investigates the solidification behaviour of the Ag-Cu eutectic alloy melt undercooled up to 100 K. It is revealed that lamellar eutectics grow in a dendritic form in the Ag-Cu eutectic melt with undercooli...This paper investigates the solidification behaviour of the Ag-Cu eutectic alloy melt undercooled up to 100 K. It is revealed that lamellar eutectics grow in a dendritic form in the Ag-Cu eutectic melt with undercooling equal to or greater than 76 K. As undercooling increases, the remelted fraction of the primary eutectics during recalescence rises. The severe remelting and the subsequent ripening of the primary eutectic dendrites lead to the formation of anomalous eutectics.展开更多
The effect of barium on the refinement of primary aluminum and on themodification of eutectics in a hypoeutectic aluminum-silicon alloy was investigated. The resultsindicate that barium not only modifies the eutectic ...The effect of barium on the refinement of primary aluminum and on themodification of eutectics in a hypoeutectic aluminum-silicon alloy was investigated. The resultsindicate that barium not only modifies the eutectic silicon but also refines the primary aluminumand there is a relationship between the retained barium and the second spacing of primary aluminum.Experiments of barium-treated commercial Al-Si hypoeutectic alloy show that barium is a bettermodifier than sodium when there is a longer holding time.展开更多
Results presented in this paper contribute to investigation of the effect of the added Ca-Si modifier amount ( ) on the microstructure scales of granular γ-(Fe,Mn)3C eutectics such as the volume fraction (f) and di...Results presented in this paper contribute to investigation of the effect of the added Ca-Si modifier amount ( ) on the microstructure scales of granular γ-(Fe,Mn)3C eutectics such as the volume fraction (f) and diameter (d) in the austenite steel matrix composites (EAMC). Directional solidification of EAMC has been carried out using vertical Bridgman method at 50.6μms-1 with a constant temperature gradient about 800Kcm-1. The higher constitutional supercooling ahead of solid-liquid interface attributing to the larger results in the enlargement of γ-(Fe,Mn)3C coupled-zone and the increment of the nucleation rate of eutectics. Therefore, f increases with increasing . The branches of the primary austenite dendrites develop more greatly as increases, which limits the growth of eutectics. As a result, d decreases with increasing .展开更多
The high-alloyed wrought superalloy GH4975 tends to form coarse MC carbides and eutectic(γ+γ′)phases,which adversely affect the cogging and homogenization process.To provide theoretical guidance for control of MC c...The high-alloyed wrought superalloy GH4975 tends to form coarse MC carbides and eutectic(γ+γ′)phases,which adversely affect the cogging and homogenization process.To provide theoretical guidance for control of MC carbides and eutectic(γ+γ′)formation,differential thermal analysis(DTA)was utilized to investigate the effect of cooing rate(10-90℃·min^(-1))on solidification behavior and micro-segregation of GH4975 alloy.According to the thermodynamic calculation and distribution characteristics of precipitates,the MC carbides can act as nucleation sites forγdendrites,but the nucleation ofγdendrites becomes less dependent on the MC carbide primers at higher cooling rates.As theγdendrites grow,the elements including Ti and Nb gradually accumulate in the residual liquid and leads to the formation of more MC carbides near the interdendritic region.Finally,the solidification is terminated with the formation of eutectic(γ+γ′).With an increase in cooling rate,the liquidus temperature rises,but the solidus temperature decreases,and thus the solidification range is obviously enlarged.The dendritic structure is significantly refined by the increase of cooling rate.The secondary dendrite arm spacing,λ_(2),as a function of cooling rate,T,can be expressed asλ_(2)=216.78T^(-0.42).Moreover,the increasing cooling rate weakens the back diffusion of Al,Ti,and Nb,increases the undercooling,and limits the growth of precipitates.Consequently,the sizes of MC carbides,eutectic(γ+γ′),and primaryγ′significantly decrease,but the area fraction of eutectic(γ+γ′)linerly increases as the cooling rate rises.Thus moderate cooling rate(such as 30℃·min^(-1))should be selected during the solidification process of GH4975 alloy.展开更多
Green solvent pretreatment of biomass represents a promising ap-proach for enhancing the econom-ic value of lignocellulosic deriva-tives.In this study,corncob biomass was treated with a diol-based deep eutectic solven...Green solvent pretreatment of biomass represents a promising ap-proach for enhancing the econom-ic value of lignocellulosic deriva-tives.In this study,corncob biomass was treated with a diol-based deep eutectic solvent(DES)under mild conditions,facilitating efficient cellulose separation.The extracted cellulose was subsequently used to fabricate cellulose hydrogels in an aqueous zinc chloride solution.The resulting hydrogel exhibited a“water-in-salt”effect due to the high concentration of ZnCl_(2).Leveraging the antifreeze properties of sorbitol,the system demon-strated outstanding low-temperature electrochemical performance,including a broad operat-ing voltage window and an ionic conductivity of 38.4 mS·cm^(-1)at-20℃.At 20℃,the de-vice achieved an energy density of 206 Wh·kg^(-1)and a power density of 2701.05 W·kg^(-1)at a current density of 1 A·g^(-1).Moreover,the flexible zinc-ion hybrid supercapacitor(ZHSC)maintained 89%of its capacitance and nearly 100%Coulombic efficiency after 5500 cycles at 20℃.This work not only advances the development of zinc-ion energy storage devices but al-so establishes a new paradigm for the green and direct utilization of biomass-derived materi-als.展开更多
Lignocellulosic biomass is the most abundant re-newable resource on Earth,boasting advan-tages such as wide avail-ability and negative car-bon emissions.Especial-ly,efficient separation of lignocellulose into cellu-lo...Lignocellulosic biomass is the most abundant re-newable resource on Earth,boasting advan-tages such as wide avail-ability and negative car-bon emissions.Especial-ly,efficient separation of lignocellulose into cellu-lose,hemicellulose and lignin,and realizing val-orization of these compo-nents are more responsive to the development needs of biomass refinery and the green chem-istry era.This review outlines the main components of lignocellulose and briefly summerizes their utilization in chemical raw materials and energy production.It mainly focused on cur-rent advances in component separation methods of lignocellulose by organic solvents,ionic liquids and deep eutectic solvents.The design of separation methods,understanding of sepa-ration mechanisms,and optimization of reaction systems in each method are highlighted in detail.Furthermore,the ongoing challenges and future directions based on mechanism and in-dustrialization are critically discussed.Our goal is to elucidate the separation mechanisms and principles of method design,providing guidance for the development of highly efficient com-ponent separation methods of lignocellulose.展开更多
Metal organic framework(MOF) assembled with coordination bonds has the disadvantage of poor stability that limits its application in the field of stationary phase,while covalent organic framework(COF)assembled through...Metal organic framework(MOF) assembled with coordination bonds has the disadvantage of poor stability that limits its application in the field of stationary phase,while covalent organic framework(COF)assembled through covalent bonds exhibits excellent structural stability.It has been shown that the stationary phases prepared by combining MOF and COF can make up for the poor stability of MOF@SiO_(2),and the MOF/COF composites have superior chromatographic separation performance.However,the traditional methods for preparing COF/MOF based stationary phases are generally solvent thermal synthesis.In this study,a green and low-cost synthesis method was proposed for the preparation of MOF/COF@SiO_(2) stationary phase.Firstly,COF@SiO_(2) was prepared in a choline chloride/ethylene glycol based deep eutectic solvent(DES).Secondly,another acid-base tunable DES prepared by mixing p-toluenesulfonic acid(PTSA)and 2-methylimidazole in different proportions was introduced as the reaction solvent and reactant for rapid synthesis of MOF/COF@SiO_(2).Compared with the toxic transition metal-based MOFs selected in most previous studies,a lightweight and non-toxic S-zone metal(calcium) based MOF was employed in this study.PTSA and calcium will form the calcium/oxygen-containing organic acid framework in acidic DES,which assembles with terephthalic acid dissolved in basic DES to form MOF.The strong hydrogen bonding effect of DES can facilitate rapid assembly of Ca-MOF.The obtained Ca-MOF/COF@SiO_(2) can be used for multi-mode chromatography to efficiently separate multiple isomeric/hydrophilic/hydrophobic analytes.The synthesis method of Ca-MOF/COF@SiO_(2) is green and mild,especially the use of acid-base tunable DES promotes the rapid synthesis of non-toxic Ca-MOF/COF@silica composites,which offers an innovative approach of greenly synthesizing novel MOF/COF stationary phases and extends their applications in the field of chromatography.展开更多
IC10 alloy is a promising material for the applications of engine turbine blades.Fabricating and repairing of the turbine blades urgently need a sound joining technique for the IC10 alloy.The traditional transient liq...IC10 alloy is a promising material for the applications of engine turbine blades.Fabricating and repairing of the turbine blades urgently need a sound joining technique for the IC10 alloy.The traditional transient liquid phase(TLP)bonding method is difficult to achieve isothermal solidification,which tends to form brittle eutectic phases.In this study,a novel Al/BNi2 composite filler was designed.This new type of composite filler facilitates the diffusion of elements to completely dissolve or disperse the brittle eutectic structure of continuous large blocks in the TLP joint,thereby improving the room-temperature mechanical properties of the joint and increasing its average shear strength by 20%to 550 MPa.Effect of Al content and bonding temperature on microstructure and mechanical strength of the IC10/Al/BNi2/IC10 joint was investigated.Microstructure evolution mechanisms of the traditional TLP bonding method(with a pure BNi2 filler)and the novel TLP bonding method(with the Al/BNi2 composite filler)were put into comparison.The TLP joint of the new filler achieved a maximum room temperature shear strength of 570 MPa(3 wt.%Al,1100℃,2 h).展开更多
The impurities and structural cracks within spent graphite(SG)in lithium-ion battery anodes hamper lithium-ion intercalation and extraction after successive charge-discharge operations,thereby yielding poor lithium st...The impurities and structural cracks within spent graphite(SG)in lithium-ion battery anodes hamper lithium-ion intercalation and extraction after successive charge-discharge operations,thereby yielding poor lithium storage behavior.Herein,low-viscosity natural deep eutectic solvent(NDES)composed of citric acid(CA)and betaine hydrochloride was employed to remove the organic impurities in SG via a one-step benign process involving hydrogen bonds and electrostatic interactions at mild conditions of 80℃ for only 30 min.After NDES leaching under optimal conditions(molar ratio of CA to betaine hydrochloride=3:1,80℃,30 min),the as-obtained sample(denoted as BG-3)exhibited an extremely clean surface,moderately enlarged interlayer distance,and more structural defects at the edge of graphite lamellae.These features facilitated lithium-ion intercalation and withdrawal,bestowing BG-3 with remarkable activity in lithium-ion battery(LIB)recycling.For instance,BG-3 delivered a capacity of 438.6 mAh g^(-1) at a current density of 0.1 A g^(-1).Its capacity retention reached 97.9%,accompanied by a Coulombic efficiency of 99.1%,upon completing 100 cycles.A molecular dynamics simulation was employed to illuminate the regeneration mechanism for anode graphite from a theoretical perspective.It revealed that NDES exhibits lower binding energy with all contaminants compared to graphite,which is favorable for NDES to eliminate impurities from graphite surfaces.This study unveils a method of recycling SG from retired LIBs by a short eco-friendly process,providing a competitive blueprint to address the shortage of battery-grade anode graphite and to achieve carbon neutrality.展开更多
The effects ofγ-ray and electron irradiation on the microstructural evolution and mechanical properties of SnPb eutectic solder joints were investigated.Following electron irradiation,the SnO_(2)phase induced byγ-ra...The effects ofγ-ray and electron irradiation on the microstructural evolution and mechanical properties of SnPb eutectic solder joints were investigated.Following electron irradiation,the SnO_(2)phase induced byγ-ray irradiation transformed intoβ-Sn,and the dislocation density in theβ-Sn crystal decreased.Moreover,numerous point defect clusters formed in theβ-Sn crystal,some of which transformed into an amorphous phase,increasing the amorphous layer thickness.Meanwhile,electron irradiation likewise resulted in rotation of the(220)plane ofβ-Sn nanograins and reduction of SnO_(2)in theβ-Sn crystal.Additionally,upon exposure toγ-ray and electron irradiation,the average shear strength of the solder balls was initially increased by 10.10%,followed by a decrease of 3.53%and 4.77%,respectively.The plasticity and the dimple count on the fracture surfaces of the solder joint initially decreased but subsequently increased.展开更多
The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdraw...The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.展开更多
Brazing filler metals are widely applied,which serve as an industrial adhesive in the joining of dissimilar structures.With the continuous emergence of new structures and materials,the demand for novel brazing filler ...Brazing filler metals are widely applied,which serve as an industrial adhesive in the joining of dissimilar structures.With the continuous emergence of new structures and materials,the demand for novel brazing filler metals is ever-increasing.It is of great significance to investigate the optimized composition design methods and to establish systematic design guidelines for brazing filler metals.This study elucidated the fundamental rules for the composition design of brazing filler metals from a three-dimensional perspective encompassing the basic properties of applied brazing filler metals,formability and processability,and overall cost.The basic properties of brazing filler metals refer to their mechanical properties,physicochemical properties,electromagnetic properties,corrosion resistance,and the wettability and fluidity during brazing.The formability and processability of brazing filler metals include the processes of smelting and casting,extrusion,rolling,drawing and ring-making,as well as the processes of granulation,powder production,and the molding of amorphous and microcrystalline structures.The cost of brazing filler metals corresponds to the sum of materials value and manufacturing cost.Improving the comprehensive properties of brazing filler metals requires a comprehensive and systematic consideration of design indicators.Highlighting the unique characteristics of brazing filler metals should focus on relevant technical indicators.Binary or ternary eutectic structures can effectively enhance the flow spreading ability of brazing filler metals,and solid solution structures contribute to the formability.By employing the proposed design guidelines,typical Ag based,Cu based,Zn based brazing filler metals,and Sn based solders were designed and successfully applied in major scientific and engineering projects.展开更多
As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancin...As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.展开更多
Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several chall...Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.展开更多
文摘A systematical study on the relationship between the amounts of different eutectic phases especially the low-melting-point(LMP)eutectics and the hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification was performed.By controlling the concentrations of major alloying elements(Cu,Mg),the amounts of LMP eutectics at the final stages of solidification were varied and the corresponding hot tearing susceptibility(HTS)was determined.The results showed that the Al−4.6Cu−0.4Mg(wt.%)alloy,which contained the smallest fraction of LMP eutectics among the investigated alloys,was observed to be the most susceptible to hot tearing.With the amount of total residual liquid being approximately the same in the alloys,the hot tearing resistance is considered to be closely related to the amounts of LMP eutectics.Specifically,the higher the amount of LMP eutectics was,the lower the HTS of the alloy was.Further,the potential mechanism of low HTS for alloys with high amounts of LMP eutectics among ternary Al−Cu−Mg alloys was discussed in terms of feeding ability and permeability as well as total viscosity evolution during solidification.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51871183 and 51571165)。
文摘Interfacial energy anisotropy plays an important role in tilted growth of eutectics. However, previous studies mainly focused on the solid-solid interface energy anisotropy, and whether the solid-liquid interface energy anisotropy can significantly affect the tilted growth of eutectics still remains unclear. In this study, a multi-phase field model is employed to investigate both the effect of solid-liquid interfacial energy anisotropy and the effect of solid-solid interfacial energy anisotropy on tilted growth of eutectics. The findings reveal that both the solid-liquid interfacial energy anisotropy and the solid-solid interfacial energy anisotropy can induce the tilted growth of eutectics. The results also demonstrate that when the rotation angle is within a range of 30°-60°, the growth of tilted eutectics is governed jointly by the solid-solid interfacial energy anisotropy and the solid-liquid interfacial energy anisotropy;otherwise, it is mainly controlled by the solid-solid interfacial energy anisotropy. Further analysis shows that the unequal pinning angle at triple point caused by the adjustment of the force balance results in different solute-diffusion rates on both sides of triple point. This will further induce an asymmetrical concentration distribution along the pulling direction near the solid-liquid interface and the tilted growth of eutectics. Our findings not only shed light on the formation mechanism of tilted eutectics but also provide theoretical guidance for controlling the microstructure evolution during eutectic solidification.
基金the financial support of the National High Technology Research and Development Program of China (Grant No. 2009AA03Z114)the Ministry of Science and Technology of China (Grant Nos. 2011ZX04014-052, 2011BAE22B02 and 2010DFA72760)
文摘Under the cold-chamber high pressure die casting (HPDC) process, samples were produced with AM60B magnesium alloy to investigate the microstructure characteristics of the eutectics, especially focusing on the constitution, morphology and distribution of the eutectics over cross section of the castings. Attentions were also paid to study the effect of heat treatment on the eutectics in the die castings. Based on experimental analysis using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), it was determined that fully divorced eutectics consisting of c^-Mg and l%MglzA112 appeared at the grain boundary of the primary c^-Mg in the as-cast microstructure. Islands and networks of β-Mg17Al12 phase were observed in the central region of the castings, while the β-Mg17Al12 phase revealed a more dispersed and granular morphology on the surface layer. The two phases ratio β/α in the central region of the castings was approximately 10%, which was higher than that on the surface layer. Besides, the defect bands contained a higher percentage of the eutectics than the adjacent regions. After aging treatment (T6), only α-Mg phase was detected by XRD in the AM60B magnesium alloy, though a small amount of precipitated β-MgITAI12 phase was observed at the grain boundary. In contrast to the microstructure of die cast AZ91D magnesium alloy under the same T0 heat treatment, no discontinuous precipitation of the β-MgITAI12 phase was observed in AMO0B magnesium alloy die castings.
基金Acknowledgements - This project was supported by the National Natural Science Foundation of China (Grant No.50001008).
文摘A new steel matrix wear resistant composite reinforced by in situ granular eutectics can be obtained by modifying with a Si-Ce-Ti compound in the steel melt. The result indicates that the in situ granular eutectic is a pseudo-eutectic of austenite and (Fe,Mn)3C, which is formed between austenite dendrites during solidification due to the segregation of C and Mn impelled by modifying elements. The quantity of in situ granular eutectic reaches up to 8%-12% and its grain size is in the range from 10um to 20um. The austenite steel matrix wear resistant composite reinforced by in situ granular eutectic (abbreviated AGE composite) and austenite-bainite steel mains wear resistant composite reinforced by in situ granular eutectic (abbreviated ABGE composite) are obtained in the as-cast state and by air hardening, respectively. The wear resistance of the AGE and ABGE composites can be more greatly increased than that of their matrix steels under low and medium impact working condition.
基金supported by the National Natural Science Foundation of China(Nos.11790293,51871016,52061135207,51671021,51971017)the Funds for Creative Research Groups of China(51921001)+1 种基金111 Project(BP0719004)Program for Changjiang Scholars and Innovative Research Team in University of China(IRT_14R05)。
文摘1.Introduction As an ancient method for manufacturing metallic materials,casting has the advantages of low cost,high process flexibility and forming complex parts.However,due to the poor as-cast mechanical properties,various processes after casting are generally necessary for traditional metallic materials to eliminate casting defects(e.g.,voids,shrinkage cavities and elemental segregation)and improve their properties,such as rolling,forging,and heat treatment.
基金supported by the National Natural Science Foundation of China(Grant No 50571068)
文摘This paper investigates the solidification behaviour of the Ag-Cu eutectic alloy melt undercooled up to 100 K. It is revealed that lamellar eutectics grow in a dendritic form in the Ag-Cu eutectic melt with undercooling equal to or greater than 76 K. As undercooling increases, the remelted fraction of the primary eutectics during recalescence rises. The severe remelting and the subsequent ripening of the primary eutectic dendrites lead to the formation of anomalous eutectics.
基金This work is financially supported by the National Natural Science Foundation of China (No. 59631080)
文摘The effect of barium on the refinement of primary aluminum and on themodification of eutectics in a hypoeutectic aluminum-silicon alloy was investigated. The resultsindicate that barium not only modifies the eutectic silicon but also refines the primary aluminumand there is a relationship between the retained barium and the second spacing of primary aluminum.Experiments of barium-treated commercial Al-Si hypoeutectic alloy show that barium is a bettermodifier than sodium when there is a longer holding time.
基金supported by the National Natural Science Foundations of China(Grant No.50001008 and No.50271042).
文摘Results presented in this paper contribute to investigation of the effect of the added Ca-Si modifier amount ( ) on the microstructure scales of granular γ-(Fe,Mn)3C eutectics such as the volume fraction (f) and diameter (d) in the austenite steel matrix composites (EAMC). Directional solidification of EAMC has been carried out using vertical Bridgman method at 50.6μms-1 with a constant temperature gradient about 800Kcm-1. The higher constitutional supercooling ahead of solid-liquid interface attributing to the larger results in the enlargement of γ-(Fe,Mn)3C coupled-zone and the increment of the nucleation rate of eutectics. Therefore, f increases with increasing . The branches of the primary austenite dendrites develop more greatly as increases, which limits the growth of eutectics. As a result, d decreases with increasing .
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52474362,52174317 and 51904146)the General Project Funded by Liaoning Province Education Department(Grant No.JYTMS20230943)。
文摘The high-alloyed wrought superalloy GH4975 tends to form coarse MC carbides and eutectic(γ+γ′)phases,which adversely affect the cogging and homogenization process.To provide theoretical guidance for control of MC carbides and eutectic(γ+γ′)formation,differential thermal analysis(DTA)was utilized to investigate the effect of cooing rate(10-90℃·min^(-1))on solidification behavior and micro-segregation of GH4975 alloy.According to the thermodynamic calculation and distribution characteristics of precipitates,the MC carbides can act as nucleation sites forγdendrites,but the nucleation ofγdendrites becomes less dependent on the MC carbide primers at higher cooling rates.As theγdendrites grow,the elements including Ti and Nb gradually accumulate in the residual liquid and leads to the formation of more MC carbides near the interdendritic region.Finally,the solidification is terminated with the formation of eutectic(γ+γ′).With an increase in cooling rate,the liquidus temperature rises,but the solidus temperature decreases,and thus the solidification range is obviously enlarged.The dendritic structure is significantly refined by the increase of cooling rate.The secondary dendrite arm spacing,λ_(2),as a function of cooling rate,T,can be expressed asλ_(2)=216.78T^(-0.42).Moreover,the increasing cooling rate weakens the back diffusion of Al,Ti,and Nb,increases the undercooling,and limits the growth of precipitates.Consequently,the sizes of MC carbides,eutectic(γ+γ′),and primaryγ′significantly decrease,but the area fraction of eutectic(γ+γ′)linerly increases as the cooling rate rises.Thus moderate cooling rate(such as 30℃·min^(-1))should be selected during the solidification process of GH4975 alloy.
基金supported by the National Key R&D Program of China(No.2023YFA1507500)the Nation-al Natural Science Foundation of China(No.52373159)。
文摘Green solvent pretreatment of biomass represents a promising ap-proach for enhancing the econom-ic value of lignocellulosic deriva-tives.In this study,corncob biomass was treated with a diol-based deep eutectic solvent(DES)under mild conditions,facilitating efficient cellulose separation.The extracted cellulose was subsequently used to fabricate cellulose hydrogels in an aqueous zinc chloride solution.The resulting hydrogel exhibited a“water-in-salt”effect due to the high concentration of ZnCl_(2).Leveraging the antifreeze properties of sorbitol,the system demon-strated outstanding low-temperature electrochemical performance,including a broad operat-ing voltage window and an ionic conductivity of 38.4 mS·cm^(-1)at-20℃.At 20℃,the de-vice achieved an energy density of 206 Wh·kg^(-1)and a power density of 2701.05 W·kg^(-1)at a current density of 1 A·g^(-1).Moreover,the flexible zinc-ion hybrid supercapacitor(ZHSC)maintained 89%of its capacitance and nearly 100%Coulombic efficiency after 5500 cycles at 20℃.This work not only advances the development of zinc-ion energy storage devices but al-so establishes a new paradigm for the green and direct utilization of biomass-derived materi-als.
基金supported by National Key Technolo-gy R&D Program of China(2023YFD1701505)De-velopment Projects in Anhui Province(2022107020013).
文摘Lignocellulosic biomass is the most abundant re-newable resource on Earth,boasting advan-tages such as wide avail-ability and negative car-bon emissions.Especial-ly,efficient separation of lignocellulose into cellu-lose,hemicellulose and lignin,and realizing val-orization of these compo-nents are more responsive to the development needs of biomass refinery and the green chem-istry era.This review outlines the main components of lignocellulose and briefly summerizes their utilization in chemical raw materials and energy production.It mainly focused on cur-rent advances in component separation methods of lignocellulose by organic solvents,ionic liquids and deep eutectic solvents.The design of separation methods,understanding of sepa-ration mechanisms,and optimization of reaction systems in each method are highlighted in detail.Furthermore,the ongoing challenges and future directions based on mechanism and in-dustrialization are critically discussed.Our goal is to elucidate the separation mechanisms and principles of method design,providing guidance for the development of highly efficient com-ponent separation methods of lignocellulose.
基金supported by National Natural Science Foundation of China (Nos.21906124,32302202)Natural Science Foundation of Hubei Province (No.2017CFB220)Natural Science Foundation of Shandong Province (No.ZR2023MH278)。
文摘Metal organic framework(MOF) assembled with coordination bonds has the disadvantage of poor stability that limits its application in the field of stationary phase,while covalent organic framework(COF)assembled through covalent bonds exhibits excellent structural stability.It has been shown that the stationary phases prepared by combining MOF and COF can make up for the poor stability of MOF@SiO_(2),and the MOF/COF composites have superior chromatographic separation performance.However,the traditional methods for preparing COF/MOF based stationary phases are generally solvent thermal synthesis.In this study,a green and low-cost synthesis method was proposed for the preparation of MOF/COF@SiO_(2) stationary phase.Firstly,COF@SiO_(2) was prepared in a choline chloride/ethylene glycol based deep eutectic solvent(DES).Secondly,another acid-base tunable DES prepared by mixing p-toluenesulfonic acid(PTSA)and 2-methylimidazole in different proportions was introduced as the reaction solvent and reactant for rapid synthesis of MOF/COF@SiO_(2).Compared with the toxic transition metal-based MOFs selected in most previous studies,a lightweight and non-toxic S-zone metal(calcium) based MOF was employed in this study.PTSA and calcium will form the calcium/oxygen-containing organic acid framework in acidic DES,which assembles with terephthalic acid dissolved in basic DES to form MOF.The strong hydrogen bonding effect of DES can facilitate rapid assembly of Ca-MOF.The obtained Ca-MOF/COF@SiO_(2) can be used for multi-mode chromatography to efficiently separate multiple isomeric/hydrophilic/hydrophobic analytes.The synthesis method of Ca-MOF/COF@SiO_(2) is green and mild,especially the use of acid-base tunable DES promotes the rapid synthesis of non-toxic Ca-MOF/COF@silica composites,which offers an innovative approach of greenly synthesizing novel MOF/COF stationary phases and extends their applications in the field of chromatography.
基金funded by the National Natural Science Foundation of China(Grant No.U2167216,52504408,52475335)China Postdoctoral Science Foundation Funded Project(Grant No.2024M754181).
文摘IC10 alloy is a promising material for the applications of engine turbine blades.Fabricating and repairing of the turbine blades urgently need a sound joining technique for the IC10 alloy.The traditional transient liquid phase(TLP)bonding method is difficult to achieve isothermal solidification,which tends to form brittle eutectic phases.In this study,a novel Al/BNi2 composite filler was designed.This new type of composite filler facilitates the diffusion of elements to completely dissolve or disperse the brittle eutectic structure of continuous large blocks in the TLP joint,thereby improving the room-temperature mechanical properties of the joint and increasing its average shear strength by 20%to 550 MPa.Effect of Al content and bonding temperature on microstructure and mechanical strength of the IC10/Al/BNi2/IC10 joint was investigated.Microstructure evolution mechanisms of the traditional TLP bonding method(with a pure BNi2 filler)and the novel TLP bonding method(with the Al/BNi2 composite filler)were put into comparison.The TLP joint of the new filler achieved a maximum room temperature shear strength of 570 MPa(3 wt.%Al,1100℃,2 h).
基金supported by the National Natural Science Foundation of China(Project Nos.22372051 and 21406044)Australian Research Council/Discovery Early Career Researcher Award(DECRA)funding scheme(DE230100180).
文摘The impurities and structural cracks within spent graphite(SG)in lithium-ion battery anodes hamper lithium-ion intercalation and extraction after successive charge-discharge operations,thereby yielding poor lithium storage behavior.Herein,low-viscosity natural deep eutectic solvent(NDES)composed of citric acid(CA)and betaine hydrochloride was employed to remove the organic impurities in SG via a one-step benign process involving hydrogen bonds and electrostatic interactions at mild conditions of 80℃ for only 30 min.After NDES leaching under optimal conditions(molar ratio of CA to betaine hydrochloride=3:1,80℃,30 min),the as-obtained sample(denoted as BG-3)exhibited an extremely clean surface,moderately enlarged interlayer distance,and more structural defects at the edge of graphite lamellae.These features facilitated lithium-ion intercalation and withdrawal,bestowing BG-3 with remarkable activity in lithium-ion battery(LIB)recycling.For instance,BG-3 delivered a capacity of 438.6 mAh g^(-1) at a current density of 0.1 A g^(-1).Its capacity retention reached 97.9%,accompanied by a Coulombic efficiency of 99.1%,upon completing 100 cycles.A molecular dynamics simulation was employed to illuminate the regeneration mechanism for anode graphite from a theoretical perspective.It revealed that NDES exhibits lower binding energy with all contaminants compared to graphite,which is favorable for NDES to eliminate impurities from graphite surfaces.This study unveils a method of recycling SG from retired LIBs by a short eco-friendly process,providing a competitive blueprint to address the shortage of battery-grade anode graphite and to achieve carbon neutrality.
基金financially supported by the National Natural Science Foundation of China Young Student Basic Research Program(for Ph.D.students)(No.525B2069)the Fundamental Research Funds for the Central Universities,China(No.HIT.DZJJ.2025005)the National Key Laboratory of Precision Welding&Joining of Materials and Structures Research Project,China(No.24-Z-09)。
文摘The effects ofγ-ray and electron irradiation on the microstructural evolution and mechanical properties of SnPb eutectic solder joints were investigated.Following electron irradiation,the SnO_(2)phase induced byγ-ray irradiation transformed intoβ-Sn,and the dislocation density in theβ-Sn crystal decreased.Moreover,numerous point defect clusters formed in theβ-Sn crystal,some of which transformed into an amorphous phase,increasing the amorphous layer thickness.Meanwhile,electron irradiation likewise resulted in rotation of the(220)plane ofβ-Sn nanograins and reduction of SnO_(2)in theβ-Sn crystal.Additionally,upon exposure toγ-ray and electron irradiation,the average shear strength of the solder balls was initially increased by 10.10%,followed by a decrease of 3.53%and 4.77%,respectively.The plasticity and the dimple count on the fracture surfaces of the solder joint initially decreased but subsequently increased.
基金Shenzhen Science and Technology Program(JSGG20220831092800001)。
文摘The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.
基金National Natural Science Foundation of China(U22A20191)。
文摘Brazing filler metals are widely applied,which serve as an industrial adhesive in the joining of dissimilar structures.With the continuous emergence of new structures and materials,the demand for novel brazing filler metals is ever-increasing.It is of great significance to investigate the optimized composition design methods and to establish systematic design guidelines for brazing filler metals.This study elucidated the fundamental rules for the composition design of brazing filler metals from a three-dimensional perspective encompassing the basic properties of applied brazing filler metals,formability and processability,and overall cost.The basic properties of brazing filler metals refer to their mechanical properties,physicochemical properties,electromagnetic properties,corrosion resistance,and the wettability and fluidity during brazing.The formability and processability of brazing filler metals include the processes of smelting and casting,extrusion,rolling,drawing and ring-making,as well as the processes of granulation,powder production,and the molding of amorphous and microcrystalline structures.The cost of brazing filler metals corresponds to the sum of materials value and manufacturing cost.Improving the comprehensive properties of brazing filler metals requires a comprehensive and systematic consideration of design indicators.Highlighting the unique characteristics of brazing filler metals should focus on relevant technical indicators.Binary or ternary eutectic structures can effectively enhance the flow spreading ability of brazing filler metals,and solid solution structures contribute to the formability.By employing the proposed design guidelines,typical Ag based,Cu based,Zn based brazing filler metals,and Sn based solders were designed and successfully applied in major scientific and engineering projects.
基金supported by the National Natural Science Foundation of China(Nos.52130204,52174376,52202070,51822405)Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120028)+6 种基金TQ Innovation Foundation(No.23-TQ09-02-ZT-01-005)Aeronautical Science Foundation of China(No.20220042053001)Science and Technology Innovation Team Plan of Shaanxi Province(No.2021TD-17)Key R&D Project of Shaanxi Province(No.2024GX-YBXM-220)Thousands Person Plan of Jiangxi Province(JXSQ2020102131)Fundamental Research Funds for the Central Universities(Nos.D5000230348,D5000220057)China Scholarship Council(Nos.202206290133,202306290190).
文摘As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.
基金financially supported by the National Natural Science Foundation of China(No.52171046)National Natural Science Foundation of China-key programme(No.52234010)the Fundamental Research Funds for the Central Universities and Shaanxi Provincial Key Science and Technology Innovation Team(No.2023-CX-TD-14).
文摘Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.
